-
8/10/2019 D2 Final Apr 99
1/61
Deliverable D2Review of current practice for assessment of
structural condition
and classification of defects
Status (P)
BRIME
PL97-2220
ProjectCoordinator: Dr R J Woodward, Transport Research
Labortory (TRL)
Partners: Bundesanstalt fuer Strassenwesen (BASt)
Centro de Estudios y Experimentacion de Obras Publicas
(CEDEX)
Laboratoire Central des Ponts et Chausses (LCPC)
Norwegian Public Roads Administration (NPRA)
Slovenian National Building and Civil Engineering Institute
(ZAG)
Date: March 1999
PROJECT FUNDED BY THE EUROPEANCOMMISSION UNDER THE TRANSPORTRTD.
PROGRAM OF THE4th FRAMEWORK PROGRAM
-
8/10/2019 D2 Final Apr 99
2/61
II
Review of Current Practice for Assessment of StructuralCondition
and Classification of Defects
by Lojze Bevc, Slovenian National Building and Civil Engineering
Institute (ZAG) Brigitte Mahut, Laboratoire Central des Ponts et
Chausses (LCPC) Knut Grefstad, Norwegian Public Roads
Administration (NPRA)
Deliverable D2P97-2220
-
8/10/2019 D2 Final Apr 99
3/61
III
CONTENTS
Page
EXECUTIVE SUMMARY 1
ABSTRACT 31.0 INTRODUCTION 32.0 OBJECTIVES OF CONDITION
ASSESSMENT OF BRIDGE
STRUCTURES 43.0 REVIEW OF CONDITION ASSESSMENT PROCEDURES 53.1
Austria 5
3.1.1 Present procedure 53.1.2 Proposed new evaluation function
for damage assessment 93.2 Denmark 93.3 France 123.4 Germany
153.4.1 Method for evaluation of damage and conditions in
accordance with RI-EBW-PRF, 1994 Edition 163.4.2 New technique for
the evaluation of damages and bridge condition 193.5 Norway 253.6
Slovenia 343.6.1 Present procedure 343.6.2 Proposed modified method
for condition rating 393.6.2.1 General 393.6.2.2 New rating
function 393.7 United Kingdom 42
3.8 United States 464.0 CLASSIFICATION OF DEFECTS 485.0
RECOMMENDATIONS 516.0 CONCLUSIONS 54Bibliography 56APPENDIX 1:
Evaluation key for new German proposal 58
-
8/10/2019 D2 Final Apr 99
4/61
1
EXECUTIVE SUMMARY
SCOPE
Europe has a large capital investment in the road network
including bridges, which are the mostvulnerable element. As bridges
age, deterioration caused by heavy traffic and an
aggressiveenvironment becomes increasingly significant resulting in
a higher frequency of repairs and possibly a reduced load carrying
capacity.
The purpose of this project is to develop a framework for the
management of bridges on theEuropean road network that enables
bridges to be maintained at minimum overall cost i.e. takingall
factors into account including condition of the structure, load
carrying capacity, rate of deterioration, effect on traffic, life
of the repair and the residual life of the structure.
SUMMARYThis report is giving an overview of procedures used in
some European countries and in theUnited States for condition
assessment of bridge structures. It is the first one of the
tworeports which are going to be delivered by the WP 1 -"Condition
assessment". The mainobjective of this work package is to derive
general guidelines and/or recommendations for condition assessment
of reinforced and pre- or post-tensioned concrete bridges.
The first chapter of the report discusses the role of condition
assessment of existing bridgestructures in a Bridge Management
System (BMS). Chapter 2 is dealing with the objectives
for condition assessment and the main causes of deterioration of
roads and bridges as themost vulnerable part of a road network. It
is emphasised that usual lack of funds for proper and regular
maintenance is consequently an important reason for delayed
interventionsaffecting further deterioration and higher repair
costs.
In Chapter 3 an overview of condition assessment procedures in
some participating Europeancountries (Austria, Denmark, France,
Germany, Norway, Slovenia, United Kingdom) and inthe United States
is presented. It comprises types of inspections to be carried out
at prescribed intervals, with short descriptions of the scope and
method of inspection, and themain features of condition assessment
procedures used in those countries. The overview for each country
includes the main structural components and their constituent
elements whichneed to be inspected and the main groups of
characteristic defects or damage types whichshould be taken into
account for the condition evaluation. Finally, the presently used
and insome countries (Austria, Germany, Slovenia) also newly
developed condition rating methodsare shortly presented.
Chapter 4 contains a general survey and classification of the
most common defects. Thesurvey is based on existing national
documents for bridge inspection and conditionassessment, submitted
by the partners. Namely, condition assessment is based on a number
of classified defects related to distinct causes and appearing on
specific elements or componentsof a structure.
-
8/10/2019 D2 Final Apr 99
5/61
2
In the last two chapters recommendations and conclusions for
further work are made aimingat the improvement of the bridge
inspection and condition assessment procedures in Europe.
IMPLEMENTATION
This review of condition assessment procedures is the basis for
the discussion and further work within Workpackage 1 which should
result in delivering of guidelines for quantitativeevaluation of
defects and for condition assessment of bridge structures. It
should alsostimulate further improvements of existing national
assessment procedures and/or development of new ones.
Some results of this review can also be used in the Workpackage
6 "Prioritisation" and in theWorkpackage 7 "Systems for bridge
management". Namely, the optimisation of repair options and the
prioritisation of candidate bridges highly depend on a reliable
conditionassessment.
-
8/10/2019 D2 Final Apr 99
6/61
3
REVIEW OF CURRENT PRACTICE FOR ASSESSMENT OF STRUCTURAL
CONDITION ANDCLASSIFICATION OF DEFECTS
ABSTRACT
Procedures for the assessment of the actual condition of
existing bridges implemented insome European countries, partners in
this project, and in the United States, are presented.
Theimportance of bridge structures in the road network and their
vulnerability to deterioration,which can not be avoided, is
stressed. Some causes of deterioration and their influence on the
progressing deterioration are also shown. Different methods for the
evaluation of bridgecondition and the possible further uses of
these rating values are discussed. The defects to be
checked and evaluated on individual bridge members for the
condition assessment are alsodiscussed.
An overview of condition assessment procedures in some
participating European countries(Austria, Denmark, France, Germany,
Norway, Slovenia, United Kingdom) and in the UnitedStates is made.
Types of inspections to be carried out at prescribed intervals are
explainedand short descriptions of the scope and procedure of
inspections are given. The need toconsider the results of condition
assessment in the design of new structures is alsoemphasised.
In the conclusion some recommendations are made for the
development of harmonisedinspection and condition assessment
procedures in Europe.
1.0 INTRODUCTION
Infrastructure networks of roads and railways play a very
important role in the everyday lifeof a country and its people.
They provide mobility and enable people to reach their destinations
as quickly and safely as possible, and they play a great role in
transportation of
goods. For these reasons it is important that the infrastructure
network maintains itsfunctionality with as little inconveniences as
possible. To achieve this goal regular maintenance, repair and/or
rehabilitation operations must be carefully planned and executedat
the proper time. As the available budget funds are very often
constrained for this kind of work, it is very difficult or
sometimes even impossible to keep the bridge stock in goodworking
condition.Bridges, as the very important part of the transportation
network, are especially vulnerable toconstant and serious
deterioration. Deterioration of bridges is the consequence of:
- poor planning maintenance operations,
-
lack of funds for regular maintenance,- poor design, detailing
and execution of the structure,
-
8/10/2019 D2 Final Apr 99
7/61
4
- underestimation of the role of proper and in time maintenance
in the past,- environmental impact,- ageing processes,- increased
length of the network and volume of the traffic,- increased volume
of bridge stock,- increased axial loads on roads and railways.
Aware of the rising problems associated with the available funds
for preservation of thefunctionality, safety, load carrying
capacity and satisfactory condition of bridge structures,Road
Authorities in many European countries have implemented various
types of databases.The aim of these databases has been to help Road
Authorities in making decisions regardingthe activities to be taken
to preserve or improve the condition of the bridge stock in
thecurrent budget year or in certain period of time. These
databases usually provide data about bridge inventory and condition
of bridges. In earlier times these data were stored on codedsheets
and as such were very impractical for implementation. With
development of
computers, and especially the PCs, the databases became larger
and are storing greater amount of data, which can be manipulated in
different ways and for different purposes. The possibility of
manipulation of bridge data for specific purposes is the basis for
development aBridge Management System (BMS). Each BMS is composed
of several modules, which can be exploited, on the basis of demands
and wishes of users and their technical capabilities, for updating
already acquired data and for storing additional and new ones. One
of the mostimportant parts of a BMS is the condition assessment
module. It can provide data about thecondition or improvement of
each element of the structure or the structure as a whole, andalso
about the progress of the revealed deterioration processes. These
data can be used later also for the assessment of the load carrying
capacity and durability of the structures as well asfor the
decision making about the procedures to preserve satisfactory
safety and stability of the structure in certain period of
time.
2.0 OBJECTIVES OF CONDITION ASSESSMENT OF BRIDGESTRUCTURES
The main objective of the condition assessment of bridge
structures is to detect adeterioration process already in its
initiation phase and to investigate and determine thecauses of
deterioration. The purpose of monitoring the progress of
deterioration processes oneach important part of a bridge
structure, with respect to their intensity and extension of
damages, is to take the right decisions in the right time. These
decisions should then befollowed by actions aiming at preservation
of condition of the structure within acceptablelimits by
appropriate maintenance activities or repair work.
Another objective is to evaluate the efficiency of different
repair techniques and thesuitability of different material used in
repair work, and to verify the right mode of application. The
results of the assessment can be also used for verification of
different siteand laboratory test methods and measurement
techniques, which have been developed for reliable assessment of
the prevailing deterioration process and prediction of its
further
progress, or for checking the efficiency of the repair work.
-
8/10/2019 D2 Final Apr 99
8/61
5
Reliable assessment of the condition of a bridge structure or of
its deteriorated parts can bemade, and the progress of
deterioration can be followed only by regular inspection of
thestructure at proper time intervals. For this reason several
types of inspection are used which,when carefully performed, can
bring very a useful results.
The initial or the reference inspection of newly built bridges
is also very important. It must bemade in the extent, which allows
at later inspections detection and recording of
progresseddeterioration. In respect to the assessed condition also
some relevant tests and measurementscould be carried out in this
scope.
Procedures for condition assessment of bridge structures, in
order to follow up and monitor their condition, have been developed
in many countries. They differ from each other inseveral aspects,
and also in the way of expressing the final condition rating. In
somecountries such procedures are used already for a longer time,
in some others the methods arein the phase of improvement on ground
of users needs and past experience, and somecountries are
developing new or modified procedures. In the following chapter a
review of procedures for condition assessment from several
countries is given, together with their abilities, role in the BMS
and envisaged improvements or changes.
3.0 REVIEW OF CONDITION ASSESSMENT PROCEDURES
The review of procedures for condition assessment and
classification of defects is made for seven European countries and
USA, on the basis of the available publications, proceedingsand
other official documents, and from personal contributions of some
participants in thisBRIME project. The aim of this review is to
provide an insight into the existing procedures,their common
features and significant differences.
3.1 Austria3.1.1 Present procedure
In 1987 the Austrian Ministry for economical affairs issued
"Procedures for assessment theextent of bridge rehabilitation", in
which the procedures and instructions for the conditionassessment
of bridge structures are described(1). To obtain useful data about
the condition of
the bridge stock, a systematic inspection of bridge structures
is implemented. In the bridgestock all bridge structures with spans
over 2m are included. Three types of inspections arecarried
out:
- Superficial inspection, which is carried out by maintenance
personnel during their regular control drives. The report is made
only in case when damages or improper function of some parts of the
bridge are observed, mainly in connection with the bridge
surface,railings, drainage system, but rarely with the main
structural components.
- General inspection, which is carried out by trained personnel
under supervision of a
bridge engineer. It is carried out every two years. General
inspection is also carried out
-
8/10/2019 D2 Final Apr 99
9/61
6
after exceptional events like earthquakes, floods, landslides,
after long periods of hightemperature, etc. At general inspection
only the accessible parts of the bridge areinspected. Report on the
assessed condition of the bridge shall be made after
eachinspection.
- Major inspection is carried out every six years. The aim of
the major inspection is toobtain detailed information about the
condition of the whole bridge and of allcomponents, to assess the
functionality and load carrying capacity of the bridge, and
torecommend regular and urgent maintenance work, load restrictions
and the delay untilnext major inspection. For these reasons all
parts of the bridge must be accessible bysimple or special devices.
Report on the assessed condition of the bridge shall be made.
The condition of the whole reinforced and/or prestressed
concrete bridge structure isdescribed by 12 characteristic
categories of damages, related to the main bridge elements.These
categories are:
Damages of the concrete surface, divided into two main
categories: damages caused by poor workmanship, damages occurring
during usage of the structure.
These damages are divided into 7 categories, which are shown in
table 1.1.
Table 1.1
category Description0 No damages1 Deterioration of cement crust
or of thin layers of concrete cover,
without any voids2 Deterioration of thin layers of concrete
surface up to 1 mm deep, thin
scars in concrete surface, partly loose fine sand grains3
Heavier deterioration of concrete surface layer up to 4 mm
deep,
scars in concrete surface, loose larger sand grains4 Damages of
concrete surface up to 10 mm deep, loose large sand
grains, scaled cement mortar between grains5 Cracks in concrete
cover along reinforcement, rust products along
reinforcement6 Delamination of concrete cover, revealed
reinforcement
Cracks because of surcharges, concentrated loads, settlement or
displacement of supports, corrosion of reinforcement, etc. The
intensity of cracks is classified by widthinto three categories: w
0.2 mm, 0.2 < w 0.4 mm, w > 0.4 mm.
-
8/10/2019 D2 Final Apr 99
10/61
7
The intensity of cracks in prestressed concrete structures in
the direction of tendons shall be: w 0.1 mm and 0.2 mm.
Open joints between the segments of free cantilever structures
or launched segmentalstructures. The same classification of the
intensity of cracks in joints as for other cracks isapplicable.
Damages of the reinforcement caused by thin concrete cover or
progressing corrosion process. They are divided into six categories
shortly described in table 1.2.
Table 1.2
category description0 No corrosion1 Light corrosion on the
surface (air corrosion), average depth of corrosion
< 0.1 mm (depth of pitting excluded)2 Light to medium
corrosion, thicker layers of corrosion products, average
depth of corrosion is between 0.1 mm to 0.3 mm (depth of
pittingexcluded)
3 Heavy corrosion, thick detached layers of corrosion products,
averagedepth of corrosion is between 0.3 mm to 1 mm (depth of
pitting excluded)
4 Very heavy corrosion, thick detached layers of corrosion
products,average depth of corrosion is greater than 1 mm (depth of
pittingexcluded)
5 Very heavy corrosion with thick detached layers of corrosion
products,
average depth of corrosion is greater than 1 mm (depth of
pittingexcluded), the cross section of the reinforcement is
significantly reduced
Post-tensioned tendons -defects are caused by corrosion.
Wetting of the concrete surface is caused by damaged
waterproofing membrane,defective drainage system, defective sealing
of the joints, etc.
Bearings - damages depending on the type of bearings are caused
by poor workmanship,improper installation, weathering, excessive
deformations, etc.
Eexpansion joints - damages are caused by deterioration of
waterproofing membrane,mechanical damages due to heavy traffic
loads, poor maintenance, etc.
Carriage-way - damages are classified into eight categories and
described according tothe cause of damage (swelling, loosening of
the matrix compound, local damages of the joints, temperature
effects, fatigue due to traffic loads, permanent deformations -
wheeltracks, presence of water, crushing of the material).
Drainage system.
-
8/10/2019 D2 Final Apr 99
11/61
8
Bridge equipment: railings, safety barriers, traffic signs,
lamp-posts, etc.
Landscape around the bridge structure: slopes in the riverbanks,
embankment slopes, etc.
The assessed condition of the bridge structure is expressed by
the condition rating S, which ingeneral form is given by the
following function:
where individual numerical attributes refer to:Gi - Type of
damage. There are 32 types of damages. The value of Gi is in the
range
of 1 to 5 and depends on the severity of the damage. For each
type of damage adescription of its extent, intensity and urgency of
the intervention on particular structural member is given.
K 1i - Extent of damage. It is expressed by numerical values
between 0 and 1. It can bedescribed by words: few or some, frequent
and very frequent or large. Thedescription usually refers to one or
more components of the bridge or to thewhole bridge structure. The
extent is never quantified by the measured sizes(length, area,
etc.) of the damage.
K 2i - Intensity of damage. It is expressed by numerical values
between 0 and 1. It can be also described by words: little or
insignificant, medium, heavy and veryheavy. The description of
intensity is usually associated with the description of damage
(e.g., width of the cracks, etc).
K 3i - Importance of the structural component or member. Values
range between 0 and1. The structural components are classified as
primary, secondary and other parts.
K 4i - Urgency of intervention. Values range between 0 and 10
and depend on the type,seriousness and risk of the collapse of the
structure or its part.
According to the obtained value of condition rating S bridge
structures can be ranked intoone of six classes, which are defined
in table 1.3.
Table 1.3
Damageclass Definition
Condition ratingvalue S
1 No or very little deterioration 0-32 Little deterioration 2-83
Medium to severe deterioration 6-134 Severe deterioration 10-255
Very severe deterioration 20-70 (k 4=10)
6 Very severe or total deterioration >50 (k 4=10)
=32
14321 iiiii k k k k GS
-
8/10/2019 D2 Final Apr 99
12/61
9
3.1.2 Proposed new evaluation function for damage
assessment(2)
A new evaluation function is proposed in order to express the
condition of the structure in anonlinear form. The overall
evaluation value S should be interpreted as "percentage of
usefulfitness" and not as the damage category. The proposed
function is expressed by
The attributes k 1, k 2 in k 3 have the same meaning and should
all be in the same range between0 and 10.
3.2 Denmark The Danish Road Directorate uses for the management
of the bridge stock on highways andmotorways the DANBRO database
system. The goal of this system is to assist the decisionmakers at
maintaining the bridge stock in the desired condition at the lowest
possible cost(3).One of the main activities for proper decision
making is to obtain data of the condition of bridge stock. On
highways and motorways bridges with the span of 5 m(4) or greater
undergoregular inspection procedures. The main activity to obtain
valuable data for the conditionassessment of the bridge structure
or bridge stock is regular inspection of bridges (3,5,6,7).Three
types of inspections are carried out:
- Superficial or routine inspection, where only major damages or
abnormal conditions areconsidered. This inspection is carried out
during the regular maintenance work withinshort intervals.
- Principal (major) inspection is carried out by well-trained
engineers. It is a visualinspection of all accessible parts of a
bridge structure. Normal inspection intervals are 3years, however,
depending on the condition of the bridge, this interval may be in
the arange of 1 to 6 years. Important damages on all components of
the bridge are registeredand rated. In the report the time of the
next principal inspection is recommended, andspecial inspection can
be required in case of poor condition of the bridge.
- Special inspection is a detailed inspection of the whole
bridge structure or only part of it.This inspection is carried out
on the basis of the recommendation of the principalinspection or on
the basis of the ranking list. A thorough investigation is
performedcombined with on-site and laboratory tests. The type and
extent of deterioration or deficiencies are established together
with their causes and the influence on further deterioration. This
type of inspection must always be carried out before rehabilitation
or replacement work, unless the extent of the damage is
insignificant and the optimum repair strategy is obvious. The
results of special inspection are used for deciding about
theoptimum repair strategy and to determine the priorities for
repair or rehabilitation, in case
of lack of funds.
222 32132
1iii
i
i k k k GS ++= =
-
8/10/2019 D2 Final Apr 99
13/61
10
Table 2.1
Component Description1 Bridge in general2 Wing walls (wing walls
and possible retaining walls)
3 Slopes (slopes with slope protection, adjacent to the
abutments and wingwalls)4 Abutments (abutment structure with back
wall, bridge seat, visible parts of
the footings)5 Piers6 Bearings (bearings on abutments and
piers)7 Slab8 Waterproofing9 Girders/beams (main girders, cross
beams, diaphragms, bracings,)10 Parapet/railing (parapets, guard
rails and railings)11 Bridge surface (normally the surface between
the curbs)12 Crossing passage13 Expansion joints (all components of
expansion joints including special
overlays adjacent to the joint)14 Drainage system15 Other
elements (bridge components, which are not included in the
previous
mentioned 12 components)
Damages which often require special inspection are:
- Slab:- Leakage of waterproofing after 25 to 30 years- Failure
of expansion joint
- Superstructure:- Reduced load capacity due to deterioration of
concrete members.
- Substructure- Chloride attack on columns, piers and abutments
due to use of de-icing salt on
motorways.
The condition is evaluated for 15 standard components of a
bridge structure, one of theevaluation components refers to the
general condition of the bridge. In table 2.1 all bridgecomponents,
which have to be considered in the evaluation process of the
condition, aregiven.
For each component the type of damage must be assigned. The
extent of the damage isestimated on site, if possible with the help
of geometry data from the inventory. Thecondition rating is a
numerical value, which describes the condition of the observed
component of the bridge structure. In the table 2.2 description
of condition ratings is given.
-
8/10/2019 D2 Final Apr 99
14/61
11
Table 2.2
category Definition0 No or insignificant damage1 Small damage
but no need of repair except routine maintenance
2 Some damage, repair needed when convenient. Component is
stillfunctioning as originally designed3 Significant damage, repair
needed very soon4 Serious damage, repair needed at once5 Ultimate
damage, total failure or risk of total failure of the component
It is assumed that inspectors should be capable of assessing the
degree of deterioration and todecide which parts of the bridge need
close investigation. For each component are given:typical types of
damages expected to occur, a description of each particular type of
damage in
case that the condition rating value equals 3, and a description
of minor maintenance andstandard repair works for some types of
damage. When the condition rating is 3 or more, arepair work must
normally be notified. For standard damages a list of standard
repairs exists.
When the condition of all components is evaluated, the condition
of the whole bridge isassessed on the basis of these values. The
highest (most unfavourable) condition ratingassigned to one of
components is not necessarily the condition rating of the whole
structure.The final assessment of the structure should identify the
damaged components, type andextent of damages, expected development
of the damage and its influence on the traffic flowand safety. The
general rule is that the condition rating for the whole bridge can
not be higher than the one assigned to the most deteriorated
component and cannot be lower than the oneassigned to either of
main components, like abutments, piers, bearings, slabs and
girders.
3.3 France
On the French road network all bridges with the spans greater
than 2 m are subject to regular inspection and condition
assessment(8). Its purpose is to provide adequate and
up-to-dateinformation about the condition of the bridge stock.
There are several types of inspection or survey performed on French
bridges.
The main inspection levels are:- Annual check (superficial
inspection). It is a brief inspection carried out on all bridges
in
the bridge stock each year at the same time as the routine
maintenance operations. Theresult of the survey is a report with
identification of the bridge, date of checking andobserved
anomalies and signs of change.
- Assessment inspection. This is a rapid visual inspection of
all accessible parts of the bridge. The result of inspection is the
bridge classification according to the IQOA method(IQOA /Image
Qualit des Ouvrages d'Art/ - Image of Bridge
Quality)(9,10,11,12,13). IQOAdefines the methodology for
classification the bridge condition. It is based on
severaldescriptive catalogues of defaults for different types of
structures. There are 25
-
8/10/2019 D2 Final Apr 99
15/61
12
catalogues in total. Inspection is carried out on all bridges of
the bridge stock every threeyears (one third of the stock each
year). The assessment is based on the inspectionaccording to the
IQOA method, and laid down in the report of standard format. If
adetailed inspection has been conducted during the year, the
assessment by the IQOAmethod is made on the basis of the report of
detailed inspection.
- Detailed periodic inspection. It is carried out on medium and
great bridges in principleevery six years. Modifications of the
inspection intervals are possible: 9 years for thestructures in
best condition, 3 years if necessary, 1 year for the most
vulnerable. This typeof inspection must be directed and carried out
by a qualified engineer with specialtraining in bridges and bridge
pathology. For the detailed inspection all parts of the bridgemust
be accessible. A report of detailed inspection should give a
detailed insight into thecondition of the bridge.
Detailed inspections of specific level are carried out in
specific cases like:
- Preliminary inspection - to define a reference state. It is
conducted when a bridge isopened or after major repair works have
been carried out.
- End of guarantee inspection to check the condition of the
bridge before expiration of theguarantee (10 years), or at the end
of the period of responsibility.
- Exceptional inspection - to check the condition of a bridge in
case of specificcircumstances (severe anomaly, start of the work in
the vicinity, natural disasters likeearthquakes, floods, fires,
landslides, etc)(14,15,16).
Other monitoring activities are:
- Continuous monitoring conducted by the qualified maintenance
staff.
- Intermediate continuous monitoring, if justified by the
condition of the bridge or if thereis an uncertainty about the
presence of deficiencies.
- High level monitoring, when observed deficiencies threaten the
safety and strength of the
structure, or its important part.
Standard forms for inspection reports have been developed for
the inspection of the mostusual types of structures. They are
designed to enable the personnel without specific trainingfor
bridges to classify various defects. The report also contains
graphic data about themorphology of the bridge and a list with
systematic diagrams of all defects which may be present.
The condition assessment of a bridge is made either on the basis
of the report of detailedinspection conducted in the year of
periodic survey or on the basis of visual "IQOA"
-
8/10/2019 D2 Final Apr 99
16/61
13
inspection. The IQOA method was designed to achieve separate
assessment of different partsof the bridge. There are three main
parts of the bridge, which are shown in table 3.1.
Table 3.1
Main part of the bridge Description Constituent parts1 Equipment
Placed above and below the bridge like pavements,
footpaths, barriers, cornices, drainage systems, pavement and
footpath expansion joints, etc.
2 Piers and bearings Columns, walls, foundations, bearings3 Deck
Slab, longitudinal girders, transverse beams, cantilever
slab; waterproofing layers, facings, etc.
During the inspection each part of bridge shall be inspected and
the severity rating shall be
assigned to each detected defect. These defects are described in
the catalogue of defects for different type of bridge structures.
In the catalogue the defects are numbered and graphically
presented. Each defect should be described and classified with
respect to its cause, origin andintensity. In table 3.2 the main
defects or damages are shown.
For the condition rating only a small number of classes is used.
The summary of the IQOAcondition rating classification is given in
table 3.3.
When the observed structural defects or deficiencies can
endanger the safety of users andurgent treatment is required, the
bridge is given an "S" rating in addition to one of the
fivecondition classes defined in table 3.3.
-
8/10/2019 D2 Final Apr 99
17/61
-
8/10/2019 D2 Final Apr 99
18/61
15
The class assigned to a piece of equipment, a protection device
or inspected part of thestructure depends on the highest rating
given for all the defects it possesses. The lowest classascribed to
one of the constituent parts of the bridge is governing also the
overall conditionclass of the bridge.
3.4 Germany
In Germany the condition of the bridge structures is presently
registered in accordance withthe existing set of guidelines(17).
The monitoring of structures in accordance with DIN 1076consists of
several types of inspections or observations:
- Superficial inspection intends to detect major faults. It is
usually performed on aquarterly basis and by the annual inspection.
It is carried out to check the functionality of expansion joints,
bearings, drainage systems and safety barriers. Annual
visualinspection of all accessible parts of the bridge is performed
to detect major defects thatmay occur.
- General inspection is carried out every three years. It
consists of visual inspection andsimple test without any specific
test equipment of all parts of the bridge, which areaccessible
without any special devices.
- Major inspection is carried out every six years. At this type
of inspection the access of all parts of the bridge must be
provided. At very large structures access is provided withspecial
devices. Beside a visual assessment also some field test for
material examinationshould be executed by specific test equipment.
The first major inspection is carried out before the bridge
structure is handed over to the traffic. The second major
inspection iscarried out before the expiration of the guarantee
period, which is 5 years. After thisinspection the regular interval
for major inspection is six years.
- Special inspection is carried out if necessitated by the
results of structural monitoring.The intention of this inspection
is to obtain a more in-depth view of some particular damage or of
the deterioration process.
- Testing and monitoring of mechanical as well as electrical
equipment is in accordance of special regulations.
The results of monitoring and testing are documented in a test
report. This report forms partof the construction register, which
must be prepared for each individual structure. Alreadyduring the
design phase files are created for the purpose of documenting all
structural detailsof importance for maintenance.
In Germany a new approach to the condition assessment of bridge
structures was developedand it is integrated in a new version of
RI-EBW-PRF (issued 1998). In the following twochapters the present
and the new method for condition assessment are shortly
described.
-
8/10/2019 D2 Final Apr 99
19/61
16
3.4.1 Method for evaluation of damage and bridge condition in
accordance with RI-EBW-PRF, 1994 Edition (18,19)
The document RI-EBW-PRF, 1994 edition, which was the basis for
condition assessment of bridge structures in Germany until 1998,
contains rules for simple and standardized recordingof bridge
condition or its part. The main part of this documentation
comprises catalogues for coding of components, damages, extent of
damage and evaluation of individual occurrencesof damage by degrees
of severity.
The edition 1994 does not contain a detailed explanation of the
degrees of severity. However in the 1988 edition the degrees of
severity and maintenance requirements were described asfollows:
1) Minor damage/faults, no risk posed to safety or durability.
Maintenance not yet required.
2)
Damage/faults which would impair the durability of the structure
in the long term.Maintenance required.3) Damage/faults which are
likely to impair safety. Maintenance required urgently.4)
Damage/faults which pose an obvious threat to safety. Immediate
action required.
Specification of the degree of severity of damage thus not only
indicates the traffic safety,stability and durability of a
structure, but also the urgency of the maintenance.
The bridge structure is divided in eight main parts, which are
further subdivided intoconstituent components and sub-components.
The main parts of a bridge are shown in table4.1.
Table 4.1
Main part of the bridge Description Main constituent parts
1 Superstructure Slabs, voided slabs, girders, box girders,
transverse beams, etc
2 Substructure Foundations, abutments, piers, columns3 Bearings
Roller bearings, fixed bearings, reinforced
elastomeric bearings, pot bearings, etc4 Expansion joints
Modular joints, rubber joints, waterproofingmembrane, etc
5 Bridge surface Carriage-way, sidewalk, curbs, sealing joints,
etc6 Safety structures Safety barriers, parapet walls, etc7
Equipment/railings Railings, drainage systems, signs, etc8 Moving
structures Lifting bridge, rolling bridge, etc
Damages are described according to the material the component of
the structure is made of.The catalogue is too comprehensive to
describe damages in the frame of this review. Just for example:
-
8/10/2019 D2 Final Apr 99
20/61
17
- cracks of concrete structures are divided in four classes
regardless of their cause (width of crack w is < 0.1 mm; w <
0.2 mm; w = 0.2 mm - 0.5 mm; w > 0.5 mm);
- wheel tracks (wt) in the pavement are divided into three
categories (wt = 0.5 - 1.0 cm; wt= 1.0 - 3.0 cm; wt > 3.0
cm).
The instructions for the condition assessment of the whole
bridge structure, which take intoaccount the effects of damage on
traffic safety, stability and durability, are presented in
table4.2. To allow a more precise determination of trends over
several inspection cycles, it is possible to specify every
condition grade by a one decimal point number. In the table
someexamples of the condition rating are given.
Table 4.2
Conditionrating Description Examples of the condition
ratingevaluation
1.0 - 1.9 The structure exhibits no or onlyslight occurrences of
damage,which do not - individually or as a whole - impair the
stability,traffic safety or durability of thestructure.
Regular maintenance is required.
- Soiled visible surfaces.- Evidence of slight
unevenness/crushing/ track grooveson road surfaces.
- Minor alluvial deposits and erosion.- Soiled/illegible traffic
signs referring
directly to the structure.
2.0 - 2.9 The structure exhibits
occurrences of a damage whichdo not impair stability or
acutelyimpair traffic safety. However,long-term durability is
notensured.
Maintenance and repair worksare required.
- Minor damage to railings and their
corrosion protection- Minor damage to riverbanks andside-slope
stabilisation, embankmentsteps, water drainage facilities, road
joints, joint sealing and masonry.
- Moderate unevenness/crushing/track grooves on road
surfaces.
-
8/10/2019 D2 Final Apr 99
21/61
18
Table 4.2 continued
Conditionrating Description Examples of the condition
ratingevaluation
3.0 - 3.9 The structure exhibitsoccurrences of damage which
-individually or as a whole - arelikely to impair the
stabilityand/or traffic safety of thestructure in the near future.
Thisdamage considerably impairs thedurability of the structure.
Itmight become necessary torestrict usage of the structure inorder
to fully restore trafficsafety.
Extensive repair work isrequired.
- Major unevenness/crushing/track grooves on road surfaces.-
Damage to seals, joint sealing,
drainage facilities, etc., which mightlead to considerable
consequentialdamage.
- Corrosion accompanied by attenuatedcross sections of
reinforcements.
- Damage indicating partial failure towithstand loads
(deformation, crackson bending sections, coupling joints,etc.).
- Railings, protective devices,coverings and other structural
fittingsexhibiting damage which could impair their
functionality.
- Exposed or ungrouted tendons, rusty prestressing steel
components.
- cracks at the level of prestressingelements.
4.0 The structure exhibits
occurrences of damage which -individually or as a whole -impair
the stability and/or severely affect the traffic safetyof the
structure.Durability of the structure is nolonger ensured.Extensive
repair work andrestoration is required.
- Failure of prestressing elements.
- Major damage to main stress-bearingelements, indicating
partial failure towithstand loads.
- Railings, protective devices and other structural fittings
exhibit damages,which considerably impair their functionality.
- Components exhibit damages which pose a high risk to traffic
in the formof falling objects or protrudingsections, which restrict
clearance for upper and lower passageways.
Described condition rating in the table 4.2 serves as an easy
means for evaluation of theengineering structures, with the view:-
To draw attention to the critical progress of deterioration of the
structure.- To support requirements concerning budget allocation.-
To compare the maintenance requirements of individual
administrations.
-
8/10/2019 D2 Final Apr 99
22/61
19
The technique of structural inspection used so far in accordance
with RI-EBW-PRF ischaracterised by detailed recording and
assessment of individual occurrences of damage andfaults. In
practice, identical occurrences of damage are evaluated
differently. Furthermore,there is no unique relationship between
the evaluation of damage and assignment of conditionratings. On the
contrary, condition evaluation applies only to overall structure.
Although theevaluation is derived from individual inspection
results, it is based in the final analysis onsubjective opinion of
the inspector. For these reasons a new technique of condition
recordingand evaluation was developed and is presented in the
following chapter.
3.4.2 New technique for the evaluation of damages and bridge
condition(18)
The new technique is based on a detailed evaluation of
individual occurrences of damage.Every occurrence of damage
detected during structural inspection performed in accordancewith
DIN 1076 must be evaluated separately in accordance with the
criteria for "trafficsafety", "stability" and "durability". In
addition, the extent of every occurrence of damagemust be
registered in qualitative terms like "small", "medium" and
"large".
For this purpose, a new technique for damage and condition
evaluation has been newlydeveloped with respect to the technique
used so far in accordance with the 1994 edition of RI-EBW-PRF.
Separate degrees of severity have been defined as follows for
damage/faultson engineering structures as specified by DIN 1076 in
accordance with the criteria of "stability", traffic safety" and
"durability".
For each definition of damage in terms of stability, traffic
safety and durability a descriptionfor each grade (0,1,2,3,4) of
damage evaluation is given.
To ensure a standard approach for the evaluation of damages,
inspection teams will beequipped with catalogues containing
detailed examples of damage evaluation.
For this new method ranges for condition ratings have been newly
defined, taking intoaccount the effects of damage on stability,
traffic safety and durability of structures. Preciselyspeaking, a
conversion has been made from the 4-stage evaluation method (rating
1 to 4) tothe 6-stage evaluation method (rating 1 to 6). This
6-stage rating of bridge condition isdescribed in table 4.3. The
new rating grades are advantageous, if compared to the former
4-stage rating system, because they allow for warnings and
establish operational thresholds in
accordance with the precepts of the German Pavement Management
System. They can beconsidered as the cornerstone for preparing
standardized techniques of damage evaluation.
-
8/10/2019 D2 Final Apr 99
23/61
-
8/10/2019 D2 Final Apr 99
24/61
21
Table 4.3 continued
Conditionrating Description
3.5 - 4.0 Inadequate structural condition.The stability and/or
traffic safety of the structure are considerably impaired or
negated.The durability of the structure might no longer be assured.
Proliferation of damage or occurrence of consequential damage might
negate stability and/or traffic safety in the short term, or lead
to an irreversible decay of the structure.Routine maintenance is
required.Repair work or replacement is required
immediately.Measures for reconstruction, warning signs for
upholding traffic safety or restrictions of usage might be
immediately necessary.
The condition rating of the overall structure Zges is a function
of the 3-stage damageevaluation set involving the parameters SV
(traffic safety), SS (stability) and SD (durability),taking into
account a defined evaluation key as well as the total extent of
damage U and thenumber of individual occurrence of damage n:
Zges = f(SV,SS,SD,U,n).
For a new method of condition rating assessment a structure is
divided in the followingcomponent group:- Superstructure-
Substructure- Prestressing elements- Foundations- Ground and rock
anchors- Bridge cords and cables- Bearings- Road- Joints-
Carriage-way surface- Caps (Bridge concrete surface)- Protective
facilities- Miscellaneous items
Each component group can be broken down into smaller components
or structural members.In table 4.4 a short summary of the new
catalogue for the standardized evaluation of damageson concrete
superstructure and some other elements is presented, including
short descriptionand subdivision of some characteristic
damages.
Table 4.4
-
8/10/2019 D2 Final Apr 99
25/61
22
Damage description S V DConcrete superstructures :- Different
kind of dirt on the visible concrete surface (graffiti, soot,
soil);- Appearance of the concrete surface (coarse grained
segments);- Concrete cover on bottom surfaces of superstructures is
too low( 3.0
3.9 cm; up to 3.0 cm, high-quality of the concrete; up to 3.0
cm, low-quality of the concrete);
- Carbonation front reaches support reinforcement;- Occasional
or large-scale exposure of the reinforcement; traces of rust
stains; minor, advanced attenuation of the reinforced
cross-section;- Corrosion of the reinforcement due to the
carbonized concrete cover
(not applicable to prestressing steel sections);Substructures:-
different kind of dirt on the visible concrete surface (graffiti,
soil);
-
formation of moss and resulting absorption of moisture;- open or
cracked masonry joints;- breakage and splintering of stones on
faced brickwork;- pervasion by moisture on individual sections, on
a large-scale or
complete pervasion of masonry or concrete and reinforced
concretesections;
Prestressing:- occasional exposure of tendons;- ungrouted
tendons (prestressing steel is not corroded or exhibits only
traces of superficial rust; steel exhibits traces of initial
corrosion;corroded prestressing steel formation of scars);
- failure of prestressing elements);Foundation: - partial or
large-scale of scouring of foundations;
Bearings:- soiled roller bearings (movement still possible);-
impermissible slant of deformed bearings;- first traces of
corrosion on bearings;
Road joints:- soiled (movement still possible) and heavily
soiled (restricted
movement);
Caps (concrete surface):- cracks (width w is
-
8/10/2019 D2 Final Apr 99
26/61
23
Table 4.4 continued
Damage description S V D- Protective facilities:
-
inadequate thickness of anti-corrosion coatings on railings;-
damage caused by corrosion (tiny spots of initial rust; attenuation
of cross-section);
- railings and/or crash barrier are missing;- railing cord is
missing (with or without imposed speed limit of
50km/h);- deviation of the railing heights (up to 5 cm and from
5 to 10 cm from
regulations);- deviation of web-member spacing from regulations
(up to 2 cm; more
than 2cm);- deviation of crash barrier from regulations (up to 5
cm and more than
5 cm);- deviation of curb's height from regulations (up to 3 cm
and more than3 cm);
- - -
Fittings:- splintered or missing steps on embankment
stairways;
Carriage-way surface:- subsidence in the backfill area (up to 2
cm - slight and more than
2 cm - considerable);- wheel tracks (depth < 1 cm; depth 1 to
2 cm; depth > 2 cm);
Terrain, vegetation, measurement points, markings:- restriction
of clearance;- damage caused by erosion on embankments (not in the
region of
foundation);- damage of the riverbanks in the vicinity of
pillars, signs of the
scouring;- alluvial deposits (alteration of the flow
cross-section; considerable
attenuation of flow cross-section);- inadequate signposting of
carrying capacity or other traffic-related
limitations;
Evaluation key for this procedure is given in the Appendix 1 of
this report.
In the process of evaluation of the condition rating for
component groups ZBG, for eachindividual occurrence of damage a
condition number Z1 is ascertained. The value Z1 issupplemented by
a positive or negative valueZ1, which takes into account the total
extent of the damage U. Extent of damage U is described as
follows:- U = "small" Z1 = -0.1;- U = "medium" Z1 = 0.0;- U =
"large" Z1 = +0.1;
-
8/10/2019 D2 Final Apr 99
27/61
24
The condition rating of the component group ZBG is based on the
maximum correspondingnumber Z1, taking into account a positive or
negative valueZ2 for the number of occurrenceof damage n within the
component group. ValueZ2 for the substructure component
groupis:
-
n < 5 Z2 = -0.1;- 5=< n =< 15 Z2 = 0.0;- n > 15 Z2 =
+0.1;
and for all other component groups:- n < 3 Z2 = -0.1;- 3=<
n =< 5 Z2 = 0.0;- n > 5 Z2 = +0.1.
The condition rating of an overall structure Zges is based
finally on the highest conditionrating of the component
groupsmaxZBG taking into account a positive or negative valueZ3for
the extent of damage to different component groups:- 1 to 3 damaged
component groups Z3 = -0.1,- 3 to 7 damaged component groups Z3 =
0.0,- more than 7 damaged component groups Z3 = +0.1.
Intermediate values are interpolated along a straight line by
the program system.
-
8/10/2019 D2 Final Apr 99
28/61
25
3.5 Norway (20,21)
Structures in the Norwegian road network owned by the Public
Roads Administration areconsidered to be bridges when the
accumulated spans or total length equals or exceed 2.5 m.Those are
regularly inspected. The inspection types reflect the thoroughness
and frequency of inspections. The bridge inspection cycle starts
when construction is complete at which pointthe following
inspection types shall be performed:
- Acceptance inspection- Guarantee inspection.
An acceptance inspection with associated measurements and
materials investigations shall be
the first inspection to be performed on the bridge. Acceptance
and guarantee inspection arealso performed on existing bridges
after a major repair or renewal.
After bridges have been handed over, routine inspections shall
be carried out for the rest of the bridge's service life. This
involves the following inspection types:
- General inspection- Major inspection- Major inspection of
cables- Major inspection under water
To compliment these inspections, or in the event of
extraordinary occurrences there may be aneed to perform:
- Special inspection.
Acceptance inspection
The purpose of the Acceptance inspection is to uncover any
deficiencies, damage or defectsto the structure which have arisen
during the construction phase, as well as identifyinginappropriate
design solutions and any sources of deterioration that may be of
significance inconjunction with future maintenance. Act as a basis
for accepting a hand over or not. Check the quality of the
maintenance work and act as a basis for accepting these or not.
An acceptance inspection is to be undertaken before or
simultaneously with the handing over of new bridges, or after the
maintenance/renewal of existing ones have been completed.
Acceptance inspections should include a visual check of the
entire bridge together with anysupplementary measurements and
materials investigations as indicated below. For new bridges major
inspections under water or of cables may also be required.
-
8/10/2019 D2 Final Apr 99
29/61
-
8/10/2019 D2 Final Apr 99
30/61
27
these activities. A major inspection is generally required every
fifth year for bridges. The firstmajor inspection shall be
performed at the required interval after the end of the
claimsdeadline.
If a bridge has suffered damage whose potential for development
remains unknown, then far more frequent than normal inspections
should be considered. These intervals must bedetermined for each
case and adapted for the bridge in question. Some significant
conditionsto consider include: traffic volume, proportion of heavy
traffic, bridge type and size,significance of the road network, low
load carrying capability, condition and damagedevelopment that
might lead to too low capacity, bridges exposed to flooding or
erosion.Bridges older than 50 years should have major inspection at
least every fifth year. Checkingmachinery etc. on movable bridges
should normally be made simultaneously with routineservicing.
Intervals for these are determined individually in each case.
In special occasions it is possible to increase the intervals
depending on total bridge lengthand bridge type. It is granted that
the person responsible for the bridge management, consider this
when a major inspection is carried out. Maximum interval between
each generalinspection is then:
- 10 years for bridges with span less than 10 m without
streaming water underneath,- 5 years for bridges with span less
than 10 m with streaming water underneath,- 5 years for bridges
with span equal or greater than 10 m,- 3 years for movable
bridges.
Major inspection will include a close visual check of the entire
bridge structure. Major
inspections can be supplemented with measurements and material
investigations as necessaryto assess the bridge's condition.
Major inspection of cables
The purpose is to undertake a check of the condition of cables,
hangers with connections andanchoring to verify their
functionality. Determine any maintenance needs and make
costestimates for these activities. Major cable inspections shall
be performed every fifth year.
Cables with uncertain damage development should be considered
inspected more often thanthe general five year interval. Intervals
must be determined in each case adapted to the bridgein question
and taking into consideration traffic volume, proportion of heavy
traffic, bridgetype and size, significance of the road network, low
load carrying capability, state anddevelopment of damage leading to
reduced capacity.
Major inspections of cables shall include a close visual check
of cables, hangers withconnections and anchoring. The inspection
shall be supplemented by measurements andmaterial investigations
where necessary to assess the condition of these elements.
-
8/10/2019 D2 Final Apr 99
31/61
28
Major under water inspection
The purpose of this inspection is to check the condition of any
foundations under water andthat of the bottom to ensure that they
are functional. Determine the need for maintenanceactivities and
make cost estimates for these.
The general requirement is that major inspections under water
shall be carried out every fifthyear. Foundations exposed to
erosion or undermining should be considered for inspectionmore
often than is generally required. The timing must be determined in
each case, adapted tothe structure in question. In special cases
extended intervals for major under water inspections may be
accepted. This applies to foundations bedded in rock, or where
there is norisk of erosion and scour. The precondition for this is
that the Bridge Division considers it to be safe. An under water
inspection of such foundations will be undertaken during
thecompletion inspection, guarantee inspection and the initial
major inspection. This does notapply to foundations where damage
has been observed.
Major under water inspections shall include a close visual check
of foundations and the bottom. The inspection shall be supplemented
by measurements and material investigationsto the extent required
to assess the condition of the foundations.
Special inspection
The purpose is to investigate closer any damage, movement and/or
deterioration observedduring previous inspections or from notes
made. Describe any costly and/or complicatedactivities, which might
be anticipated.
Special inspections may be considered in the following
situations: previous major inspectionshave proven the need,
accidents such as collision, overloading, flood or flooding,
whenexperience with similar types of bridges and environment
indicates so.
A special inspection is normally undertaken of particularly
exposed or damaged elements, butmay also encompass the entire
bridge. It may include a visual check, measurements or materials
investigations or a combination of these.
During the inspection, a description of observed
damages/deficiencies in various elementsshall be prepared. An
assessment shall be made on how the damage/deficiency could
affecteach element and a bridge as a whole and impact of the
damage. For a uniform descriptionstandard types of damages are
described in "Inspections Handbook for Bridges". The locationof
each damage/deficiency on the bridge and/or element should also be
recorded.
The degree of damage is measured by a numerical scale used to
give a technical assessmentof the magnitude of the
damage/deficiency; that is, whether maintenance activities must
beexecuted or not, and if so, how soon. In the table 5.1 the codes
for the degree of damage are presented.
-
8/10/2019 D2 Final Apr 99
32/61
29
Table 5.1
Code Description1 Slight damage/deficiency, no action required2
Medium damage/deficiency, action needed during next 4 - 10 years3
Serious damage/deficiency, action during the next 1-3 years4
Critical damage/deficiency, immediate action required or within
year at the
latest9 Not inspected
The impact of the damage is represented by a letter code used to
indicate the consequencesany damage/deficiency might have on the
bridge, bridge users and/or environment. The codesare presented in
the table 5.2.
-
8/10/2019 D2 Final Apr 99
33/61
30
Table 5.2
Code DescriptionB Damage/deficiency threatening load carrying
capability
T Damage/deficiency threatening traffic safetyV
Damage/deficiency that may increase maintenance costsM
Damage/deficiency that may affect the environment/aesthetics
The results of measurements and materials investigations shall,
along with inspections, formthe basis for establishing the degree
of damage and the consequences of the damage. Thecodes for the
degree and the consequence of the damage shall be used together
when damageis to be assessed (e.g., 3B - serious damage/deficiency
that can reduce bridge carryingcapability if it remains untouched
for more than 1-3 years. Action required within 1-3 years).
For each damage type the activating condition is described in
"Inspections Handbook for Bridges". The term activating conditions
means that a structure or an element has suffereddamage or
developed faults or deficiencies that require maintenance soon. The
activatingcondition must be determined when inspecting bridges,
that is, what can be accepted andwhat will require action. This
shall be indicated using the degree of damage in the
followingmanner:- Degree of damage 1: condition may be accepted
without action.- Degree of damage 2-4: condition will require short
or long-term action (up to 10 years).
If possible, the cause of the damage should be reported (not
claim for General inspection).
The condition assessment of the bridge is based on the
assessment of individual bridgeelements. For this reason the bridge
is divided in elements like expansion joints, bearings,drainage
systems, rails, pavement and watertight membrane, superstructure,
columns,abutments, etc.
In the table 5.3, 5.4 and 5.5 evaluation of some typical damages
of concrete structures(cracks, spalling, corrosion) is
described.
-
8/10/2019 D2 Final Apr 99
34/61
31
Table 5.3 - Cracks (only concrete members are described)
Causes:- Design mistakes leading to too low load carrying
capacity- Poor materials leading to shrinkage of concrete, AAR,
etc.- Construction mistakes as poorly vibration and curing- Lack of
maintenance as for instance blocked joints with restricted
movements- Corrosion of the reinforcement- Settlement- Traffic
loads- impact loads
Measurements, material investigations:- Crack width (w) and/or
pattern- Removal of concrete cover in some local areas in order to
observe the condition of the
reinforcement- Structural microscopy on concrete cores in order
to detect AAR Degree of damage/consequence of damage:
Degree of damage must be considered depending upon the crack
width w, number and pattern of cracks, the cause(s) and expected
future development of the cracks. Thelocation of bridge, its age
and the prevailing environment which influences further
deterioration must also be considered.
Usually cracks in concrete will affect the future maintenance
costs. The degree of damagecould be determined in this way:
Minor aggressive environment: w
-
8/10/2019 D2 Final Apr 99
35/61
32
Table 5.4 - Spalling (only concrete members are described)
Causes:- Design mistakes. Bearings too close to the edge of
vertical wall on abutments for
instance, faulty reinforcement- Construction mistakes as lack of
concrete cover leading to corrosion and spalling- Prevailing
environment causing carbonation or chloride penetration, corrosion
and
spalling- Loads- Impact loadsDegree of damage/consequence of
damage:Degree of damage/consequence must be considered depending on
size of the spalling, thelocation and the expected future
development.Spalling may influence the load carrying capacity in
elements carrying compression. It will
disturb the bond and anchoring of the reinforcement. This will
have influence on the loadcarrying capacity.Spalling because of
corrosion may increase maintenance costs if the damages are
notrepaired.Spalling will threat the traffic safety if spalled
concrete could fall down on peopleunderneath the bridge.Spalling
may affect the environment/aesthetics making poor impression of the
bridge andthe users feeling unsafe. The degree of damage should
reflect the way the bridge affects thesurroundings and the
impression given bypassing people.
Activating condition:Spalling that has caused reduced load
carrying capacity should be repaired as soon as possible.
Spalling that will reduce the load carrying capacity if it goes
further should be repaired before the load carrying capacity is too
low.
Spalling that may fall down and cause damages on people should
be repaired immediately.
Spalling that affects the environment/aesthetics should be
repaired if this gives a poor impression of the bridge and the
damage(s) is clearly visible to the public.
-
8/10/2019 D2 Final Apr 99
36/61
33
Table 5.5 - Corrosion (only concrete members are described)
Causes:- Design mistakes. Lack of cover, improper concrete
mixture, improper construction
details.- Material fault - improper mixture.- Construction
mistakes as lack of concrete cover or concrete cover of bad
quality
leading to corrosion.- Prevailing environment, carbonation or
chloride penetration causing corrosion.- Impact load could cause
spalling and corrosion.
Degree of damage/consequence of damage:Degree of
damage/consequence must be considered depending on amount of the
corrosion,the effect on the load carrying capacity and the expected
future deterioration.Pre- or post-tensioned reinforcement is very
vulnerable for corrosion and essential for the
carrying capacity. Degree of damage should be considered to be 3
or 4.Elements that are very vulnerable due to corrosion as the
superstructure or slender columnsshould be given a high degree of
damage. In environments with a high humidity, corrosionwill
progress rapidly and affect the load carrying capacity after a
short period of time. Thedegree of damage must reflect this.
Corrosion leading to spalling could also affect the loadcarrying
capacity because the distribution of stress is disturbed.Corrosion
in massive columns, abutments, etc. normally have a minor effect on
the loadcarrying capacity. The degree of damage should be
low.Degree of damage must reflect the anticipated future
deterioration and related maintenancecosts.Corrosion will cause
spalling that may affect the environment/aesthetics making a poor
impression of the bridge and the users feeling unsafe. Degree of
damage should reflect theway the bridge affects the surroundings
and the reactions of passing by people.Activating
condition:Corrosion that has caused reduced load carrying capacity
should be repaired as soon as possible.Corrosion that will reduce
the load carrying capacity if it goes further should be repaired
before the load carrying capacity is too low.Corrosion that will
affect future repair costs should be repaired before costs
increaseconsiderably.Corrosion that affects the
environment/aesthetics should be repaired if this gives a poor
impression of the bridge and the damage(s) is clearly visible for
the public.
-
8/10/2019 D2 Final Apr 99
37/61
34
3.6 Slovenia3.6.1 Present procedure
At the moment Slovenia has no official regulation or guideline
for carrying out theinspections and procedures for assessment of
the condition of bridges. In the existingregulation22 there are
only two articles dealing with the maintenance of structures. The
firstarticle emphasises that concrete and reinforced concrete
structures must be maintained asspecified in the design documents
and that safety and functionality shall be preserved. Thesecond
article requires that bridges must be visually inspected every two
years, and specialattention shall be paid to cracks, deformations
and damages that are essential for the safety of the structure. If
the inspection reveals that the safety level of the structure is
lower thandesigned, deflection must be checked by the load
test.
In the early eighties the Road Administration has made the first
complete inventory of all bridges, under its jurisdiction. One of
the main results of this inventory was thecomprehension that a more
systematic approach is needed to acquire useful data for
bridgemanagement and maintenance. For this reason a research work
was undertaken in 1986through 1988 by the Slovenian National
Building and Civil Engineering Institute. The maingoal of this work
was the survey of current practices for the inspection and
assessment of bridges in several European countries, and to prepare
some basic guidelines for theassessment of the condition of
bridges, managed by the state Road Administration.
The result of this work is a three-volume report23 which was
later the basis for theimplementation of regular inspection and
assessment of the condition of bridges. In the 1st
volume the compilation of current practice for the assessment
and inspection of bridges fromseveral countries was presented. The
2nd and 3rd volume contained tables with sketches and photos of
characteristic damages on different parts of a bridge structure,
and short descriptionof their possible causes. In 1990 a
methodology24 was developed for determination andselection of the
capacity reduction factor, figuring in the expression of the rating
factor RF.
In Slovenia, the whole inventory of bridges, viaducts, over and
underpasses with spans of 5m or longer has been regularly inspected
since 1990. The tunnels are also included in theinventory and in
the system of inspection. The following types of inspection are
carried out at
indicated intervals:- Superficial inspection is carried out by
maintenance personnel at least once a year. It
consists of the visual check of condition of some visible
components of the bridge, like pavement, railings,
expansion-joints, etc. This inspection is part of regular
maintenanceactivities which are carried out by the maintenance
personnel.
- General inspection is carried out every two years by trained
personnel guided by thestructural engineer. The inspection consists
of visual examination of all accessible parts of the bridge without
using special equipment. Inaccessible parts of the bridge may
beinspected by binoculars. The report of general inspection
comprises coded descriptions of bridge components and elements,
type, extent and intensity of detected damages. Thelocation of
distinctive damage is described with reference to the inspected
element or
-
8/10/2019 D2 Final Apr 99
38/61
35
component. The recommendations for maintenance, repair work,
major inspection at anearlier time than regular interval, or for
special inspection with field measurements or laboratory tests are
also stated. The condition rating of four main bridge components
andof the entire bridge is then computed on the basis of the
estimated intensity and extent of each damage type and the impact
of each affected bridge element on bridge safety.
- Major inspection is carried out every six years. The
inspection consists of visual check of all bridge elements. For
this reason the access by ordinary or special equipment must be
provided to every part of the bridge. All damages must be assessed
from close distancewhich assures satisfactory estimation of the
extent, intensity and type of the damage. Thereport is set up in
the same scope and format as for the general inspection. A part of
major inspection is also underwater inspection of foundations and
riverbed around foundations.For bridges on highways major
inspections are obligatory also before their handover to
thetraffic, before the expiration of the guarantee period and after
every substantial repair work.
- Special inspection is carried out when recommended after a
major or general inspection.The purpose of this in-depth
inspection, which is basically carried out on the distressed parts
of a bridge, is the thorough examination and assessment of the
extent, intensity, typeand cause of previously detected damages.
Within its scope all detected damages must befirst carefully
mapped. The damaged spots must be examined by field
measurements(thickness of the concrete cover, concrete strength
with rebound hammer, electrochemical potentials, concrete
permeability, remaining cross section of the reinforcement
andconcrete sections, depth of carbonation, etc..) and laboratory
tests (chloride profiles,concrete alkalinity, concrete strength on
concrete cylinders, metallographic andfractographic test of the
prestressed wires or strands, mechanical properties of the
prestressed reinforcement with different grades of corrosion
damages, electrochemical properties of the concrete, etc.). The
results of these examinations are used for categorisation of
detected damages and for giving general recommendations about
themost suitable repair method to be applied on typical damaged
areas in reliance to the typeand category of the damage.
General or major inspections of bridges are also carried out
after major natural disasters likemajor earthquakes, floods, fires,
landslides, etc. The scope of these inspections depends onthe
importance of the bridge, its size and its accessibility.
The condition of the bridge is expressed by the condition rating
for every main bridgecomponent and for the entire bridge, the
latter being simply the sum of all componentcondition ratings. In
table 6.1 the main components of the bridge to be considered in
bridgerating and their main constituent parts are given.
-
8/10/2019 D2 Final Apr 99
39/61
36
Table 6.1
Component Constituent parts
Substructure Landscape around bridge structure, riverbed,
foundations, supportingmembersSuperstructure Superstructure,
tunnelBridge surface Bridge surfaceBridge equipment Bearings,
expansion-joints, safety equipment, drainage system
For recording and evaluation of damages the bridge structure is
divided into eleven mainelements, which are further divided into
sub-elements. They are listed in table 6.2 accordingto their
numerical codes.
Table 6.2
Elementcode
Elementdescription Sub-elements
100 Landscape around bridge structure
Approaching carriage-ways, approaching embankment or excavation,
lining of embankment or excavation slopes,drainage systems of the
embankment or excavationslopes,
200 Riverbed Riverbed within and outside the area of the
bridge,riverbanks, lining of riverbank slopes,
300 Foundations Single or strip footings, piles, pile caps,
caissons400 Supporting
structuresAbutments, wing-walls, retaining walls on
approachingramps, piers, single or multicolumn supports, caps over
columns,
500 Bearings concrete bearings, steel bearings, elastomeric
bearings, pot bearings, sliding bearings,
600 Superstructure Girders main and secondary, hollow girders,
bridgedeck slabs voided or solid, box girders with upper andlower
plate and side webs, transverse beams,
700 Bridge surface Carriage-way, sidewalks, curbs, edge
beams,
waterproofing membrane, installation shafts,800 Tunnel inner
lining, portal structure900 Expansion joints steel parts, rubber
membrane, fixing elements, 1000 Safety equipment Metallic safety
barriers, guard rails, concrete blocks,
concrete barriers, approaching guard rails, railings,columns for
public lightening,
1100 Drainage systems pipelines, lids, pipe hangers,
In table 6.3 main coded damage items, related to the
construction material, behaviour of the
structure and bridge equipment, and, the corresponding damage
types are given.
-
8/10/2019 D2 Final Apr 99
40/61
37
Table 6.3
Damagecode Damage item Corresponding damage types
0000 Deformations Vertical and horizontal displacements,
rotations,
settlement, unevenness, 0100 Surroundinglandscape
Erosion of the riverbed slopes, scour, excessivevegetation on
the riverbank slopes or embankment slopes,missing parts or damaged
linings of the slopes,
0200 Concrete Cracks (w 0.2 mm; 02 < w 0.5 mm; 0.5 < w
1.0mm; w > 1.0 mm); spalling, delamination; surfacedefects;
wetting; to low thickness of the concrete cover;mechanical damages;
etc
0300 Reinforcing and prestressing steel
Corrosion of stirrups and main steel, corrosion of prestressing
reinforcement, exposed tendons, exposedreinforcement and stirrups,
breakage of tendons or prestressing steel; etc
0400 Structural steel Damage of coatings, corrosion, cracks,
etc0500 Structural timber Moisture, fungus, moss, breakage of
timber elements,0600 Stone, brick,
plaster Cracking, spalling of mortar, protrusion of
moisture,separated bricks and stones, etc
0700 Bridge surface Wheel tracks in the pavement, damages of the
joints,deterioration of joint seals, abrasion, deterioration of
waterproofing membrane, unclean surface, etc
0800 Bearings Mechanical damages of steel parts,
excessivedeformations, blockage of movements, corrosion of
steel
parts, etc0900 Expansion joints Mechanical damages of steel
parts, deterioration of sealing elements, corrosion of steel
elements, etc
1000 Equipment Corrosion of steel elements, mechanical
damages,missing elements or parts of elements, etc
1100 Drainage systems Corrosion, missing elements, unclean
drainage system,etc
The condition rating R for assessing the condition of a bridge
structure and its components in
a quantitative form, is expressed by the following function:
The individual factors mean:
VD - damage type value.Bi basic value associated with the damage
type i. The value of Bi is within the range
of 1 to 4 and expresses the potential effect of the damage type
on the safetyand/or durability of the observed structural
element.
== iiiii D K K K K BV R 4321
-
8/10/2019 D2 Final Apr 99
41/61
38
K 1i Factor which describes the extent of the damage and is
expressed by numericalvalues between 0 and 1. In the field record
it is described by letters A, B and C(A up to 30% (or number of the
same elements), B from 30 to 60% and C for more than 60% of the
observed surface of the structure). The description usuallyrefers
to one or more components of the bridge or to the whole bridge
structure.The extent is not described by the measured sizes
(length, area, etc.) of thedamage on the affected component or
structure.
K 2i Factor which describes the intensity of the damage and is
expressed by values between 0 and 1. In the field only the
intensity grades I to IV (I light, II medium, III severe, IV very
severe) are recorded. The description of intensity is usually
related to the type of damage (e.g. width of the cracks,thickness
of the delamination, etc).
K 3i Factor which describes the importance of the structural
component or member for the safety of the entire structure. The
values range between 0 and 1.
K 4i Factor which describes the urgency of intervention. The
values range between 0and 10. The chosen value depends of the type
of structure, and seriousness andrisk of collapse of the affected
structure or its part.
According to the obtained value of condition rating R, the
bridge structure is classified intoone of five condition classes,
described in table 6.4. On this ground the main bridge inspector
will finally take decision about the global condition class of the
whole bridge structure.
Table 6.4
Conditionclass Definition Conditionrating R 1 Critical >202
Bad 14-223 Satisfactory 8-174 Good 3-125 Very good 0-5
The condition rating is used for the first ranking of the
bridges in a management system, and
for screening those bridges, which should be commissioned for
in-depth inspection, or undergo a more thorough maintenance, or
repair, or rehabilitation intervention. However, themethod has a
minor drawback, because for different types of structures (e.g.,
slabsuperstructure or superstructure made of girders, transverse
beams and deck slab) differentcondition rating values can be
obtained, even the damage types, intensities and extent
areestimated as being the same. This was the main reason, that this
method has been recentlymodified and improved.
-
8/10/2019 D2 Final Apr 99
42/61
39
3.6.2 Proposed modified method for condition rating(25)
3.6.2.1 GeneralThe above basic approach has been further
developed by introducing the following
modifications:(1) The condition rating is not expressed by the
simple sum of damage values, but by theratio between: the effective
sum of damage values obtained by taking into account, from a
closed
list of potential damage types, the damage types detected at the
inspection, and, the reference sum of damage values obtained by
taking into account from the same
closed list every damage type that could realistically occur on
the same structure,multiplied always by unit intensity and extent
factors K 2 = K 3 = K 4= 1.
Thus, the condition rating of a structure or of its observed
portion/component is definedas the fraction or percentage of a
reference rating value associated with an assumed
average condition of this particular structure. By being related
to a conventionalreference deterioration level, the rating value is
much less affected by the number of damage types, and by the number
of members composing the observed structure, or bynumber of
spans.The reference condition level is not a fixed value, but shall
always be in relation to thearrangement of the inspected structure
and to potential damages on this structure.Therefore, the reference
sum should take into account damages, which are with great
probability expected to appear on the existing members of the
observed structure, andshall ignore those damages, which can never
occur on it. E.g. to calculate the conditionrating of a reinforced
structure the reference sum shall not consider damage values
related to prestressed concrete.(2) In the case of multi-span
bridges, where the inspection is usually performed span after span,
the condition rating of the whole structure or of its main
components is expressed by the average sum of damage values
calculated for each individual span. Namely, theintensity and the
extent of the detected damages can be more adequately defined and
be better balanced when the evaluation is carried out for
individual spans.
(3) The factors to evaluate the intensity of a damage type on a
structural member arecharacterised by general descriptive criteria,
and for some damage types also bynumerical criteria. Factors to
evaluate the extent of damage on a structural componentare defined
by general descriptive criteria only. To achieve better sensibility
of ratingvalues in relation to the assessed condition, the two
factors are applied in wider ranges,
namely 0,5 - 1,0 - 1,5 - 2,0, establishing 4 intensity and 4
extent classes.3.6.2.2 New rating functionAccording to 3.6.2.1, the
condition rating of the observed structure is defined as:
RV
V C D
D ref =
,100
where:VD effective sum of damage values calculated for the
observed structure or its part (e.g.
bridge component), related to the detected damage types from a
list, (values of K 2,K 3 and K4 should be allotted according to the
newly defined ranges see 3.6.2.1),
-
8/10/2019 D2 Final Apr 99
43/61
40
VD,ref reference sum of damage values obtained by taking into
account every damage typefrom the same list that could potentially
occur on the same observed structure or its part, multiplied by
unit values of factors of intensity and extent. (K 2i = K 3i = 2, K
4i =const. = 1).
In the practical evaluation procedure the above formula is
applied in the following form:
R K M
K M C
m
k
m
m ref
k =
11
11
100
where:
M B K K K m in
i i i= 1
2 3 4 (i = 1 to n)
is by the relevant factor K 1m reduced sum of damage valuesVD,
computed for thestructural member m, (Mm = VD/K 1m), and
M B K K K m ref it
i i i, = 1
2 3 4 (i = 1 to t)
is by the respective factor K 1m reduced reference sum of damage
valuesVD, ref for thesame observed member m (Mm,ref = VD,,ref/K
1m)
k number of members m within the observed structuren number of
detected and evaluated damage types i on a member m
t total number of potential damage types on the member m (from
Table-1)
On the basis of the calculated condition rating the inspected
structure is classified into one of the deterioration classes,
described in table 6.5.
-
8/10/2019 D2 Final Apr 99
44/61
41
Table 6.5
Deterioration
class
Description of the condition, necessary intervention,
Deterioration examples ()
Rating
rangeI No defects, only constructional deficiencies.
No repair, only regular maintenance needed.(geometrical
irregularities, aesthetic imperfections,discolouring,)
0 - 5
II Low degree of deterioration, which only after longer period
of time might be the cause for reduced serviceability or
durabilityof the affected structural component, if not repaired in
proper time.Deteriorated locations can be repaired with low costs
as part of regular maintenance works.(local cracks, smaller
deficiencies resulting from badconcreting work, locally too thin
concrete cover,)
3 - 10
III Medium degree of deterioration, which can be the cause for
reduced serviceability and durability of the affected
structuralcomponent or element, but still not requiring any
limitation of use of the structure.Repair in reasonably short time
is required.(cracking, greater deficiencies resulting from bad
concretingwork, very thin concrete cove on mostly wet areas,
defects of waterproofing on bridges,)
7 - 15
IV High degree of deterioration, reducing the serviceability
anddurability of the structure, but still not requiring
seriouslimitation of use.Immediate repair to preserve the designed
serviceability anddurability is required.(reinforcement corrosion
on main carrying members, open joints, grouting deficiencies of
prestressing ducts,)
12 - 25
V Very heavy deterioration, requiring limitation of use
(e.g.restricted vehicle weight on the bridges), propping of
mostcritical members, or other protective measures.
Immediate repair and strengthening of the structure is
requiredor the carrying capacity shall be adequately reduced.(heavy
corrosion of reinforcement or prestressing tendons inthe main
carrying members, wide cracks because of overloading, presence of
water in prestressing ducts,)
22 - 35
-
8/10/2019 D2 Final Apr 99
45/61
42
Table 6.5 continued
Deterioration
class
Description of the condition, necessary intervention,
Deterioration examples ()
Rating
rangeVI Critical deterioration, requiring immediate propping of
the
structure and strong limitation of the use (e.g., closing of the
bridge).Immediate and extensive rehabilitation works are
needed,however the design serviceability and use of the structure,
aswell as acceptable remaining service life can no more beachieved
with economic costs.(as class V and lower level of safety,)
30
3.7 United Kingdom(26,27,28,29,30)
In the United Kingdom there are four main types of inspection
for all bridges with the spangreater than 3.0 m, culverts 1.8 to 3
meters span or multi-cell culverts with the cumulativespan greater
than or equal 5 m, if their cover to road surface is less than 1.0
m. In Scotlandthe minimum culvert size is 2 meters. The four main
types of inspections are:
- Superficial inspection is carried out regularly by the staff
of Maintaining Agent. It is acursory check of obvious deficiencies
which might lead to accidents or high maintenancecosts. It can be
made from ground and deck level or from any walkway or platform,
builtinto a structure. If any superficial inspection reveal a
possible defect, which should hazardto road, rail or other users,
the Maintaining Agent shall immediately take actions requiredto
safeguard the public. The overseeing organisation and the owner of
the structure shall be informed without any delay.
- General inspection is a visual examination of accessible
representative parts of thestructure, adjacent earthworks or
waterways. It can be made from ground and deck level or
from any walkway or platform, built into a structure.
Inspections are required not morethan two years after the last
General or Principal inspection.
- Principal inspection is a close examination of all inspectable
parts of the structure andadjacent earthworks and waterways. A
suitable access may need to be provided to enable aclose
examination. The inspection shall be carried out at intervals,
which normally wouldnot exceed six years, exceptionally may be up
to ten years. For the new structures it iscarried out about one
month before the issue of the certificate of Completion or opening
of the structure to traffic. In recent years limited testing has
been included(31).
-
Special in
